Radiological phantoms and other test objects are often used as objects to be imaged in radiological equipment for the following purposes:
(i) to compare different radiographic systems when considering equipment purchases,
(ii) to standardize image quality among different facilities performing similar radiological procedures,
(iii) to assist in selection of technical factors for image production,
(iv) for routine quality assurance testing, and
(v) for the teaching of the principles of image formation to residents and radiological technologists.
An anthropomorphic radiological phantom is designed to simulate the interaction of x rays with a particular anatomical site in the human body. A phantom should satisfy the following requirements:
(i) it should yield reproducible images when irradiated under identical conditions, i.e. it should not decompose or change its radiation attenuating characteristics with time,
(ii) it should produce images which can be used to assign numerical indices of imaging performance of the system being evaluated,
(iii) the images produced by the phantom should be anthropomorphic, i.e. have similar characteristics to images of human body parts which would normally be made with the system being evaluated. This is important because the radiologist who is ultimately responsible for the diagnostic quality of the images, is trained to evaluate images not by objective masurements of contrast, noise, and resolution, but by the perceptibility of anatomic structures in the body. Often such individuals have difficulties in relating results obtained using simplistic objective phantoms currently available to the quality that will be obtained in actual patient images.
There is a need for the production of anthropomorphic phantoms for radiological imaging which are more realistic than those presently available.
It is known in radiographic practice to utilize radiographic data to produce shields and compensators which are applied to patients to protect specific body parts from radiation, or to modulate radiation exposure. The data is reviewed and processed and used to cut a styrofoam mould profiled when filled with a radiation absorbent material to provide a desired pattern of attenuation to the incident radiation. The shields and protectors produced are used to control radiation dosage, not for imaging purposes, and are used in conjunction with the patient, not as a substitute.